1. Field of the Invention
This invention relates to improving the rebound characteristics of a bat for baseball or softball.
2. Description of the Related Art
Conventionally, the flying distance of a ball is thought to be extended when hit by a high strength bat. This is because it was considered that a bat with a high degree of strength has excellent rebound characteristics and the flying distance of a ball depended solely on these rebound characteristics of the bat. However, in recent years, it is understood that the flight distance of a ball which does not rely on the strength of the bat but on a bat which can reduce the consumption of impact energy as ball transformation energy when a ball and bat collide and can extend the flying distance of a ball. In addition, it is understood that the higher the rebound force of the bat itself, the further the flying distance of a ball is extended.
Thus, in order to extend the flying distance of a ball, a variety of bat structures were tried. As a first structure, as shown in Japanese Laid Open Patent 2005-305146, a method was attempted in which a number of urethane layers were arranged on the exterior of a part to be hit of a metal bat and the urethane layers reduced the consumption of impact energy as ball transformation energy. As a second structure, as is shown in 2008-29620, a method was attempted in which a double layered metal bat was formed and the consumption of impact energy as ball transformation energy was reduced by bending of the metal thin tube.
However, in the method in which urethane layers are arranged on the exterior of the part to be hit of a metal bat, because a urethane layer deteriorates by secular distortion, the durability of the bat is inferior compared to a metal manufactured bat. In addition, the bat also suffered from an increase in miss hits.
However, while a metal bat with a double layered structure has no durability problems and the flight distance of a ball is extended, it is difficult to make a light metal bat. Particularly, in the case of a child's or girl's bat, it is impossible to swing the bat unless it is light since they are weak. Generally, swing speed is largely proportional to the weight of a bat and the lighter the bat the faster the swing speed. Therefore, in the case of a child's or girl's bat, lightness is particularly demanded and further improvements in a double layered bat are also demanded. In particular, requests for lightness are predominant for female softball bats.
The present invention can reduce the consumption of impact energy as ball transformation energy and in particular aims to provide a light bat for baseball or softball. Furthermore, the present invention is easy to manufacture and aims to provide a low cost bat for baseball or softball.